Stepper Motor Absolute Position Sensing Without Startup Indexing
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Solution Overview
Problem
Existing absolute position sensing systems for stepper motors in automated luminaires are either time-consuming, noisy, or require frequent maintenance due to indexing processes and potential damage from harsh environments.
Innovation Solution
An absolute multi-turn rotational position sensing system using a combination of first and second absolute rotational sensors to detect the position of a cam indexer and an indexer wheel, allowing the control system to determine the absolute position of the luminaire mechanism without the need for indexing, thus reducing setup time and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional indexing processes are used for absolute position sensing, then position accuracy can be achieved, but setup time increases and noise is generated
Solution Approach 1:
The system performs preliminary indexing during the manufacturing process, establishing the absolute position relationship between the cam indexer and indexer wheel before deployment. This preliminary action eliminates the need for time-consuming indexing operations during field setup, while maintaining position accuracy through the pre-established mechanical relationship.
Solution Approach 2:
The patent replaces traditional mechanical indexing processes with an optical sensing system using absolute rotational sensors. These sensors optically detect the positions of the cam indexer and indexer wheel, eliminating the need for physical indexing operations that generate noise and require setup time, while maintaining measurement precision.
2Ease of operation
If traditional position sensing systems are used, then position control can be achieved, but maintenance requirements increase due to potential damage from harsh environments
Solution Approach 1:
The system replaces mechanical position sensing components that are susceptible to harsh environmental damage with optical absolute rotational sensors. These optical sensors have no moving parts that can wear or fail due to environmental factors, significantly reducing maintenance requirements while maintaining ease of position control operation.
Solution Approach 2:
The patent employs robust optical sensors that are designed to be replacement-ready components. If damage occurs in harsh environments, the entire sensor assembly can be quickly replaced as a unit, minimizing downtime and maintenance complexity compared to repairing traditional mechanical sensing systems.
3Measurement precision
If indexing processes are used for absolute position determination, then position accuracy is achieved, but noise is generated
Solution Approach 1:
The system eliminates mechanical indexing operations that generate noise by using optical absolute rotational sensors to directly measure the positions of the cam indexer and indexer wheel. The optical detection process is silent, maintaining position accuracy without generating harmful noise.
Data Source
AI summary
A luminaire includes a luminaire mechanism, a stepper motor, an absolute multi-turn rotational position sensing system, and a control system. The stepper motor moves the luminaire mechanism. The absolute multi-turn rotational position sensing system includes absolute rotational sensors that detect absolute positions of a cam indexer on the motor shaft and an indexer wheel coupled to the cam indexer. The indexer wheel rotates by a predetermined amount in response to one full rotation of the cam indexer. The control system determines an absolute position of the luminaire mechanism based on information from the absolute rotational sensors relating to the positions of the cam indexer and the indexer wheel. The control system receives a commanded position for the luminaire mechanism and causes the stepper motor to move the luminaire mechanism to the commanded position based on the absolute position of the luminaire mechanism.